In known chain transmissions including a bushingless roller chain engaged with sprockets, the chain is composed of outer and inner link plates, connecting pins and rollers. Pairs of inner link plates and pairs of outer link plates are disposed in an alternating, overlapping arrangement along the direction of travel of the chain. The pins are fixed to the outer link plates and extend through pin holes in the inner link plates and through the rollers in such a way that the inner link plates can articulate relative to the outer link plates and the rollers can rotate on the pins. Teeth on the sprockets engage with the rollers. A chain transmission using a bushingless roller chain is described Japanese patent application 1991-0349922, laid open under no. Hei 5-164196 on Jun. 29, 1993. A similar bushingless roller chain, having sets of multiple link plates in widthwise rows, is described in Japanese patent Application No. 1999-0310336, laid-open under No. 2001-124149 on May 8, 2001.
Unlike conventional roller chains, these roller chains have no bushings fixed to inner link plates and interposed between rollers and connecting pins. The rollers therefore contact the connecting pins directly. A large impact force acts on the rollers, the connecting pins, and the inner link plates when the rollers start to engage a sprocket tooth, reducing the durability of the rollers, the connecting pins and the inner link plates and generating excessive noise.
If the chain transmission incorporating a bushingless roller chain includes chain guides, an additional problem arises. If the outer and inner link plates of the chain conform to the surface of the chain guide the contact area between the chain and the guide becomes large, and results in a high frictional loss and decreased power transmission efficiency.
Accordingly, there is a need for a chain transmission utilizing a bushingless roller chain, in which the inner link plates, connecting pins and rollers have improved durability, in which power transmission efficiency is improved, and in which noise generated as the rollers engage sprocket teeth is reduced.